It is known that certain fluoroalkylphosphoric acid esters are useful as dispersing agents in the emulsion polymerization of fluoroelastomers (WO 2009/094344 A1). These esters are of the formula X—Rf—(CH2)n—O—P(O)(OM)2, wherein n=1 or 2, X=H or F, M=a univalent cation, and Rf is a C4-C6 fluoroalkyl or fluoroalkoxy group (branched or non-branched). In the first step of the synthesis of these fluoroalkylphosphoric acid esters, the phosphorodichloridate is prepared by reaction of the corresponding fluoroalkanol with phosphorous oxychloride. The di-and tri-esters are not as suitable dispersing agents as are the mono-esters in the emulsion polymerization of fluoroelastomers. Thus, it would be desirable if the phosphorylation reaction yielded exclusively the polyfluoroalkanoyl phosphorodichloridate.
Kudryavtsev, I. Yu. et al., Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2535-2540 (1982) discloses catalytic phosphorylation of a series of polyfluorinated alkanols by phosphorous oxychloride using Group I metal chlorides as catalyst. The results indicate that the LiCl catalyzed phosphorylation reaction of polyfluorinated alkanols with POCl3 produced predominantly polyfluoroalkanoyl phosphates and polyfluoroalkanoyl phosphorochloridates and very little or no polyfluoroalkanoyl phosphorodichloridate.